The efficiency of a gas turbine generally increases with increased combustion gas temperatures. However, excessive temperatures within the turbine may reduce the longevity of the airfoils in the turbine and thus increase repairs, maintenance, and outages associated therewith. As a result, various designs and methods have been developed to provide cooling to the airfoils. For example, a cooling media may be supplied to a cavity or cooling circuit inside the airfoil to convectively and/or conductively remove heat from the airfoil. In particular configurations, the cooling media may flow out of the cavity through passages in the airfoil to provide film cooling over the outer surface of the airfoil. In certain instances a thermal barrier coating is applied to the outer surface of the airfoil to enhance thermal protection and the passages extend through the thermal barrier coating.
A liquid jet guided laser system may be used to create the passages through the airfoil with a reduced risk of chipping the thermal barrier coating. However, the depth of the passages and/or the angle or aspect ratio at which the holes must be cut along the surface of the airfoil generally requires that a nozzle body of the liquid-jet guided laser system be positioned close to the surface of the airfoil. Conventional nozzles are generally cylindrical, flat faced and bulky, thus preventing or impacting precise positioning of the nozzle relative to the airfoil surface. As a result, the laser beam may not completely penetrate through the outer surface, resulting in a damaged airfoil that must be refurbished or discarded. Therefore, an improved liquid-jet guided laser system would be useful.